What's the worst mistake you can make on an ERB or ORB?

Probably falsifying it. I remember reading in the Army Times a couple years ago that a CSM that had falsely added Ranger School and a number of badges and awards.

I've always been told that everything on the ORB/ERB needs to match I.E if you wear it on your uniform (award/badge etc.) then it needs to also be in your awards and decorations section. Likewise if you completed training (including badge producing schools) and they awarded an additional skill identifier then it should also be annotated in the appropriate section. The biggest mistake a Soldier can make though is to lie. Every so often I read about about a Senior Officer or NCO that lied about earning awards and it ended their careers. Whenever I have a question the first person I ask is the S1.

The other half of this discussion are the Soldiers individual records I.E iPERMS or other service specific online database. If whatever school or decoration has been annotated on the ORB/ERB then the supporting documentation had better be in the Soldiers permenant file.

no idea